1. Field of the Invention
The present invention relates to a detecting device for detecting tire information such as air pressure or temperature of tires.
2. Description of the Related Art
A conventional tire information detecting device will now be described with reference to FIG. 7. In FIG. 7, a transmitting unit 10 is mounted to each tire of a vehicle to detects the air pressure of a tire and then transmit it as a tire air pressure signal. One receiving units 31 is disposed between front wheels A1 and A2 and another receiving unit 31 is disposed between rear wheels B1 and B2. Each of the receiving unit has a built-in receiving antenna for receiving a signal from the transmitting unit 10. A control unit 4 such as a microcomputer determines whether or not a tire air pressure value output from the transmitting unit 10 is within a normal range. A display unit 5 such as an LCD displays the information determined by the control unit 4.
A sensor for detecting tire air pressure is disposed in the transmitting unit 10. A detected air pressure is converted into a tire air pressure signal, and then a high frequency signal modulated by the air pressure signal is transmitted from the transmitting unit 10. The receiving unit 31 outputs the high frequency signal after demodulating the high frequency signal. The demodulated high frequency signal are read, and displayed as an air pressure value on the display unit 5 (see Japanese Unexamined Patent Application Publication No. 2003-002020 (FIG. 1)).
Here, if each sensor has a variation in its output property of air pressure, a correct air pressure value cannot be displayed. Further, the arrangement of four sensors having uniform output properties increases the cost.